Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Uncertainty and Fuzzy Decisions in Earthquake Risk Evaluation of Buildings
Get PDFThe Northern region of Thailand has been considered as one of the seismic risk zones. However, most existing buildings in the area had been designed and constructed based on old building design codes without seismic consideration. Therefore, those buildings are required to upgrade based on earthquake building damage risk evaluation. With resource limitations, it is not feasible to retrofit all buildings in a short period. In addition, the results of the risk evaluation contain uncertain inputs and outputs. The objective of this study is to prioritize building retrofit based on fuzzy earthquake risk assessment. The risk assessment of a building was made considering the risk factors including (1) building vulnerability, (2) seismic intensity and (3) building values. Then, the total risk was calculated by integrating all the risk factors with their uncertainties using a fuzzy rule based model. An example of the retrofit prioritization is shown here considering the three fuzzy factors. The ranking is hospital, temple, school, government building, factory and house, respectively. The result helps decision makers to screen and prioritize the building retrofitting in the seismically prone area
Forecasting Annual Solar PV Capacity Installation in Thailand Residential Sector: A User Segmentation Approach
Get PDFSolar PV is one of the fast-growing renewable energy in Thailand. Three sectors are contributing to solar PV installation, which are solar farms, industrial, and residential sector. However, the latter only contributes 1.39% of the cumulative capacity in 2016. By considering the lowering price of installation cost, growing affordable households, and a vast amount of solar irradiation in Thailand, it is of interest to observe the potential of the residential sector. Besides, there is a lack of study that focuses on the forecasting of residential solar PV in Thailand. Thus, this paper emphasizes on annual installation forecast of solar PV capacity in Thailand residential sector by using segmentation. This research categorizes residents into four categories, PV users with and without batteries, potential users, and rejecters, aimed to understand different types of users. An online survey of Thai residents about solar PV utilization was conducted from December 2017 to February 2018 to collect the data for the research. The results find that there is an exponential trend of increasing residential solar PV installation, followed by the reduction of payback period over time. It is forecasted about 3,511.4 MW of residential PV installation in the end of forecasting period. This research helps the decision maker to update the policies
Evaluation and Prediction of the Scour Depth of Bridge Foundations with HEC-RAS Numerical Model and Empirical Equations (Case Study: Bridge of Simineh Rood Miandoab, Iran)
Get PDFToday, scouring is one of the major issues in the river and coastal engineering. Each year, many bridges around the world are destroyed due to neglecting hydraulic elements. In the present study, scour depth around the piers of the Simineh Rood Bridge in Miandouab, Iran were investigated using empirical relationships and the HEC-RAS numerical model, and the results are compared with each other. Firstly, a hydraulic software model was created from the river where the bridge was located using field data. Then, by entering the scouring data of bridge piers for discharges with a return period of 5 to 1000 years, changes in flow discharge were investigated for scouring around the middle and lateral sides of the bridge. Results of the empirical equations showed that some of the equations are not sensitive to increases in flow discharge, and for each return period, the results are near each other. Also, numerical model results showed that with an increase in discharge, scouring increases in the bridge’s middle and lateral piers. In all discharges, the first and the seventh pier had the lowest and highest scour depth, respectively. Also, the left and right abutments are heavily influenced by increasing discharge. In discharges with a return period of 1000 years, the scour depth was 11.19 and 6.32 m. The Frohlich method is not as sensitive as the CSU method to an increase in discharge when calculating scour depth. Finally, the results of the numerical model were compared with experimental empirical equation
Optimal Supplier Selection Model with Multiple Criteria: A Case Study in the Automotive Parts Industry
Get PDFThis research proposes a mathematical model for supplier selection for a case-study car seat manufacturer. This research is divided into 2 parts. The first part is the raw material supplier evaluation method using Analytic Hierarchy Process. This part weights the importance of main decision criteria and sub-decision criteria, complying with part makers’ satisfaction. The result from the first part is scores for each raw material supplier resulting from multiple evaluation criteria. The second part proposes a mathematical model for supplier selection using integer programming. The scores of each supplier from the first part will be considered along with raw material consumption to select the suitable raw material suppliers that maximize overall part makers’ satisfaction. The results from the first part of this research show that the most important criterion for supplier evaluation is cost, which is about 41%. Quality, Delivery, Service, and Risk factors are approximately 24%, 14%, 12% and 9%, respectively. The result from the second part shows that the model can effectively match material suppliers to part makers according to their preferences. Comparing with current situation, the satisfaction is increased by 26% with this proposed framework. It means the proposed model can help matching the right supplier to each part maker that can increase overall satisfactions for this case-study’s supply chain
New Results on Positive Realness in the Presence of Delayed Dynamics
Get PDFPositive realness is a very important tool for the achievement of hyperstability and passivity of dynamic systems. This paper is devoted to extend some positive realness results of transfer functions in the presence of point-delayed delayed dynamics. Sufficiency-type conditions which guarantee the positive realness of delayed transfer functions under point delays are given. The value of the direct input-output interconnection gain is seen to be crucial in the performed analysis. The relevance of the results rely in the importance of the hyperstability property of closed-loop systems under non-linear and time-varying controller devices. In fact if the feed-forward controlled plant has a strictly positive real transfer function then the closed-loo system is asymptotically hyperstable , that is, globally asymptotically Lyapunov´s stable for any non-linear time-varying controller which belongs to a hyperstable class defined as that which satisfies a Popov´s type inequality
Flexural Moment Capacity Evaluation of Reinforced RPC Two-way Slabs
No full textThis paper presents calculations to determine the flexural moment capacity of Reactive Powder Concrete (RPC) two-way slabs depending on three models from previous studies (Model 1, Model 2, and Model 3). The outcomes of these calculations were compared with experimental results to tempt the accuracy and the applicability of the adopted theoretical models. The experimental program included testing three simply supported RPC two-way slabs of 1000 mm length, 1000 mm width, and 70 mm thickness. The tested specimens were of identical properties except their steel fibers volume ratios (0.5 %, 1 %, and 1.5 %). It was found out that the first model (Model 1) is the most suitable among the three models, where its outcomes were very close to the corresponding experimental data, while Model 2 was underestimated the failure load, and Model 3 was overestimated it by large differences, where the maximum difference between the theoretical and experimental failure load according to the mentioned three models was 3.4%, 48.2%, and 87.2% respectively.
 
Effects of Redundancy in Bracing Systems on the Fragility Curve Development of Steel Jacket Offshore Platform
Get PDFSteel jacket offshore platforms are typically employed for shallow to moderate water depth. During the platform operation, there are some historical accidents of the complete damages for the diagonal members of the bracing systems owing to explosion, fire and dropped objects. The different locations of damages in bracing members demonstrate different levels of risk for safety and integrity of the structures. This present research studies the effects of redundancy in the bracing systems for steel jacket offshore platforms. The assessments have been carried out by nonlinear pushover analysis method and formation of nonlinear hinges of different members were noted. Redundancy in different positions has been considered to investigate the consequences. Reserve strength ration, RSR and damage strength ratio, DSR of the global structure were also evaluated to understand the importance of different local members. From the collapse data of local failures, fragility curve for the global structure was estimated. The results demonstrated that position of damage can be a great concern which affects the overall performance of the structures.  
Structural Design for Pressure- And Temperature-Resistant Buildings
Get PDFLoads from explosions differ from seismic and wind loads due to their greater severity, continuity, rapidity, and thermal extremity. That is, explosions cause massive structural damage by exposing surrounding structures to extremely high pressure and temperature. Thus, structures at risk of explosive damage must be stronger than typical buildings in withstanding both ordinary loads and the additional pressure and temperature loads caused. Explosion-resistant structures are required in the petrochemical industry, explosive armories, power stations, and gas storage facilities, among others. This study aims to examine the structural performance of a building subject to three types of loads: (1) the pressure of 300 bars, (2) the temperature of 300 °C, and (3) the pressure of 300 bars combined with the temperature of 300 °C. The research analyzes three primary reinforced structures, namely columns, beams, and slabs, in terms of the parameters resulting from each scenario to determine a set of criteria for designing the structural components of explosion-resistant building
Antibacterial and Corrosion Resistance Properties of Anodized AA6061 Aluminum Alloy
Get PDFAnodizing is one of the surface treatments for aluminum and its alloys. It is commonly used to increase corrosion resistance and mechanical properties. This technique is also applied for decorative purpose. Therefore, anodized aluminum alloys are widely used in many applications such as household structure, cell-phone case, automobile and aircrafts. Anodic aluminum oxide (AAO) structure, which has a pore at the center of each hexagonal cell arrangement, is created after anodizing process. To further enhance the property of anodized aluminum alloys, antibacterial property can be produced on AAO surface by deposition of nanoparticles into its pore structure. In this work, AA6061-T6 aluminum alloy was anodized at 12 V using 20%w/v H2SO4 at temperature of 17±1°C for 30 minutes. AgNO3 solution was used for producing Ag nanoparticles. Effects of AgNO3 concentrations on antibacterial and corrosion resistance properties of anodized AA6061 aluminum alloy were studied. Antibacterial property was investigated on both gram-positive (S.aureus) and gram-negative (E.coli) bacteria according to JIS Z 2801 standard test for three months after exposure to ambient environment. 100% reduction of S.aureus was achieved, whereas 97.3% reduction of E.coli was obtained when using 1mM AgNO3. However, the deposition of Ag nanoparticles resulted in a slight increase in corrosion susceptibility
Startup Thailand: A New Innovative Sacrificial Anode for Reinforced Concrete Structures
Get PDFSevere damage reinforced concrete structures affected by corrosion are increasing. The study of prevention and protection technique play an important role to cope this urgent issue. Usage of different types of surface coatings on concrete/rebar are highly depend on workmanships of construction. Thus, sacrificial anodes are offered as one of the corrosion prevention technique. The discrete sacrificial anodes are comprise of zinc metal covered with a high alkalinity mortar which sacrifices itself to protect the corrosion of rebar. The key parameter of sacrificial anode in concrete is the activating mortar. It will help the overall cathodic reaction to efficiently protect reinforcing steel. Therefore, a new sacrificial anode was then accomplished in new activating mortar components. Two different activating mortar type have been established. This research investigated the performance of the new sacrificial anodes installed in the concrete prisms, slabs, and concrete water tanks in order to explore the corrosion prevention performance as per NACE [1], ISO [2] and ASTM standards [3-4]. This experimental study was tested on ASTM G109 [3], ASTM C876 [4] and small-scale water tank suffering from chloride-induced corrosion of the reinforcement. The performance of the anodes was determined at 28 days age and 365 days after installation to assure the activating time dependency for the mortar. The results of concrete prisms and slabs revealed that the anode polarized the rebar at a significant potential. For the water tank test results, two different concrete type were conducted with exposing chloride solution and assessed using close-interval potential mapping. The results showed a good agreement with enhance the structural durability